Managed PoE Switch - 4 Port (Power through spare pairs only)

Requirement #1, #4: GS110TPP - no models with less PoE+ ports and SNMP AFAIK (I'm not Netgear!)

Requirement #2, #3: SNMP controls (GS110TPP - download -> MIB -> POWER-ETHERNET-MIB) allows enable/disable PoE, reading current PSE consumption in Watt delivered to the port, reading and setting power pairs, ... Further on, there is some more information available e.g. on the PSE state diagram, negotiated power pairs

Reading (e.g. on auto negotiation) or setting the power pairs (Note: GbE does use all pairs for signals - this might allow setting the mode so you can loop-out the non-signal pairs over measuring equipment):

Requirement set to outband::

pethPsePortPowerPairs OBJECT-TYPE
SYNTAX INTEGER {
signal(1),
spare(2)
}
MAX-ACCESS read-write
STATUS current
DESCRIPTION
"Describes or controls the pairs in use. If the value of
pethPsePortPowerPairsControl is true, this object is
writable.
A value of signal(1) means that the signal pairs
only are in use.
A value of spare(2) means that the spare pairs
only are in use."
REFERENCE
"IEEE Std 802.3af Section 30.9.1.1.4 aPSEPowerPairs"
::= { pethPsePortEntry 5 }

Requirement #2:

pethPsePortAdminEnable OBJECT-TYPE
SYNTAX TruthValue
MAX-ACCESS read-write
STATUS current
DESCRIPTION
"true (1) An interface which can provide the PSE functions.
false(2) The interface will act as it would if it had no PSE
function."
REFERENCE
"IEEE Std 802.3af Section 30.9.1.1.2 aPSEAdminState"
::= { pethPsePortEntry 3 }

Requirement #3: Depending on the measurement quality, this might be already sufficient:

...
pethMainPseConsumptionPower OBJECT-TYPE
SYNTAX Gauge32
UNITS "Watts"
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"Measured usage power expressed in Watts."
::= { pethMainPseEntry 4 }

...

Enough fre consulting for now - send beer!

Regards,
-Kurt.